Poly(vinyl butyral) (PVB) is commonly used in the manufacture of polymer sheets that can be used as interlayers in light-transmitting laminates such as safety glass or polymeric laminates. Safety glass often refers to a transparent laminate comprising a poly(vinyl butyral) sheet disposed between two sheets of glass. Safety glass often is used to provide a transparent barrier in architectural and automotive openings. Its main function is to absorb energy, such as that caused by a blow from an object, without allowing penetration through the opening or the dispersion of shards of glass, thus minimizing damage or injury to the objects or persons within an enclosed area.
Poly(vinyl butyral) is commonly produced using a conventional batch process that, like most batch processes, requires repeated cycles of reactant addition, mixing, emptying, and cleaning. One conventional method can require over a four hour batch cycle time.
After poly(vinyl butyral) has been formed, washing of the poly(vinyl butyral) slurry is usually accomplished in a discontinuous wash tank, which is time and space consuming. The limitations of conventional poly(vinyl butyral) washing cause particular inefficiencies when coupled with continuous poly(vinyl butyral) production methods, such as those disclosed in copending application U.S. application Ser. No. 12/426,246. In those processes, the inability to continuously wash the continuously produced poly(vinyl butyral) slurry can result in either the need to stop continuous production or to provide substantial, inefficient storage capacity for the continuously produced poly(vinyl butyral) to allow for a conventional batch washing process to cycle.
Accordingly, further improved methods are needed to produce poly(vinyl butyral) using a continuous washing process that is efficient, scalable, and that produces washed poly(vinyl butyral) of consistently high quality.